Atomic interface regulation is thought to be an efficient method to adjust the performance of single atom catalysts. Herein, a practical strategy was reported to rationally design single copper atoms coordinated with both sulfur and nitrogen atoms in metal-organic framework derived hierarchically porous carbon (S-Cu-ISA/SNC). The atomic interface configuration of the copper site in S-Cu-ISA/SNC is detected to be an unsymmetrically arranged Cu-S 1 N 3 moiety. The catalyst exhibits excellent oxygen reduction reaction activity with a half-wave potential of 0.918 V vs. RHE. Additionally, through in situ X-ray absorption fine structure tests, we discover that the low-valent Cuprous-S 1 N 3 moiety acts as an active center during the oxygen reduction process. Our discovery provides a universal scheme for the controllable synthesis and performance regulation of single metal atom catalysts toward energy applications.

Investigating the structure, modification, interaction, and function of biomolecules in their native cellular environment leads to physiologically relevant knowledge about their mechanisms, which will benefit drug discovery and design. In recent years, nuclear and electron magnetic resonance (NMR) spectroscopy has emerged as a useful tool for elucidating the structure and function of biomacromolecules, including proteins, nucleic acids, and carbohydrates in living cells at atomic resolution. In this review, we summarize the progress and future of in-cell NMR as it is applied to proteins, nucleic acids, and carbohydrates.

and background absorption than that done in the first near-infrared window (NIR-I, 650-950 nm). [1] Therefore, the development of theranostic agents in NIR-II region has become something of a research hotspot. [1a,2] Recently, there is an ever-increasing number of papers describing the modification of gold nanomaterials for NIR-II photoacoustic imaging (PAI) and photothermal therapy (PTT) owing to its unique plasmonic, acoustic, and electric properties, as well as multifunctionality endowed by its various dimensions and morphologies. [1c,e,3] Furthermore, its excellent biosafety surpasses the limits of most inorganic nanomaterials. [4] Currently, there are few methods that shift the localized surface plasmon resonance (LSPR) peak of gold nanomaterials from NIR-I to NIR-II region. [2a,5] For instance, some gold nanorods (GNRs) with superhigh aspect ratios or GNRs with extremely thin shells have been reported. [6] However, most of them still bear poor photostability. In fact, tailoring the morphology is not the only method to obtain a redshift in the absorbance of gold nanomaterials. Substances coated to the surface of GNRs can also cause absorbance red or blueshifts. For example, Wu et al. found that a layer of Cu 2 O could cause absorbance redshift of GNRs from 600 to 800 nm. [7] Yeh et al. developed a rattle-like structure with a GNR encapsulated in a cavity of AuAg nanoshell to achieve a broad absorbance band span 300-1350 nm. [2a] However, most metal oxides suffer from biotoxicity and not responsive to tumor microenvironment. Therefore, the development of biocompatible and stimuli-responsive coatings for plasmonic modulation of GNRs remains a big challenge. Manganese is one of the most commonly used metal element in cancer theranostics on account of its good biosafety and rich quantity of valence states, which allows for the design and synthesis of intelligent theranostic agents. [8] For example, manganese dioxide (MnO 2) is widely used as a catalase to decompose hydrogen peroxide (H 2 O 2) in tumor microenvironment and produce oxygen and hence relieves the tumor hypoxia and reduces tumor resistance to radio-or chemotherapy. [9] Recently, it was reported that MnO 2 could decrease glutathione level in Nanotheranostic agents of gold nanomaterials in the second near-infrared (NIR-II) window have attracted significant attention in cancer management, owing to the reduced background signal and deeper penetration depth in tissues. However, it is still challenging to modulate the localized surface plasmon resonance (LSPR) of gold nanomaterials from the first near-infrared (NIR-I) to NIR-II region. Herein, a plasmonic modulation strategy of gold nanorods (GNRs) through manganese dioxide coating is developed for NIR-II photoacoustic/magnetic resonance (MR) duplex-imaging-guided NIR-II photothermal chemodynamic therapy. GNRs are coated with silica dioxide (SiO 2) and then covered with magnesium dioxide (MnO 2) to obtain the final product of GNR@SiO 2 @MnO 2 (denoted as GSM). The LSPR peak of GNRs could be tuned by adjust...

The recovery process of COVID-19 patients is unclear. Some recovered patients complain of continued shortness of breath. Vasculopathy has been reported in COVID-19, stressing the importance of probing microstructure and function of lungs at the alveolar-capillary interface. While CT detects structural abnormalities, little is known about the impact of disease on lung function. 129Xe MRI is a technique uniquely capable of assessing ventilation, microstructure and gas exchange. Using 129Xe MRI, we found COVID-19 patients have higher ventilation defects percentage (5.9% vs 3.7%), unchanged microstructure, longer gas-blood exchange time (43.5 ms vs 32.5 ms), and reduced RBC/TP (0.279 vs 0.330) compared with healthy subjects. These findings suggest regional ventilation and alveolar airspace dimensions are relatively normal around the time of discharge, while gas-blood exchange function is diminished. This study establishes the feasibility of localized lung function measurement in COVID-19 patients. Such readouts could be useful as a supplement to structural imaging.

Multifunctionalized and branched M-OEGs represent valuable PEGylation agents, linkers, and scaffolds in biomedicine. However, the tedious synthesis limited their availability and application. We herein present an azide reductive dimerization method for the convenient synthesis of aza-M-OEGs and derivatives, which provides easy access to a variety of multifunctionalized and branched M-OEGs in one step. With this method, hexa-arm M-OEGs with 54 symmetrical fluorines were synthesized in two steps as a water-soluble, self-assemble, 19F MRI sensitive, and biocompatible dendritic biomaterial.

We analyze whether the organizational structure of firms (i.e., whether a firm is diversified or focused) affects their cash holdings. Using Compustat firm level and segment-level data, we find that diversified firms hold significantly less cash than their focused counterparts. Our results are robust to industry adjustments at the segment level and to different factors previously found to be important determinants of cash holdings. Using time-series, crosssectional, and additional robustness tests we are able to attribute the lower cash holdings among diversified firms to complementary growth opportunities across the different segments of these firms and the availability of active internal capital markets. We find that the other theories that rely on the potentially effective use of asset sales of non-core segments of diversified firms to generate cash, and the increased agency/influence costs in diversified firms do not offer an economically significant explanation for the lower cash holdings among diversified firms.

To design a clinically translatable nanomedicine for photodynamic theranostics, the ingredients should be carefully considered. A high content of nanocarriers may cause extra toxicity in metabolism, and multiple theranostic agents would complicate the preparation process. These issues would be of less concern if the nanocarrier itself has most of the theranostic functions. In this work, a poly(ethylene glycol)‐boron dipyrromethene amphiphile (PEG‐F54‐BODIPY) with 54 fluorine‐19 (19F) is synthesized and employed to emulsify perfluorohexane (PFH) into a theranostic nanoemulsion (PFH@PEG‐F54‐BODIPY). The as‐prepared PFH@PEG‐F54‐BODIPY can perform architecture‐dependent fluorescence/photoacoustic/19F magnetic resonance multimodal imaging, providing more information about the in vivo structure evolution of nanomedicine. Importantly, this nanoemulsion significantly enhances the therapeutic effect of BODIPY through both the high oxygen dissolving capability and less self‐quenching of BODIPY molecules. More interestingly, PFH@PEG‐F54‐BODIPY shows high level of tumor accumulation and long tumor retention time, allowing a repeated light irradiation after a single‐dose intravenous injection. The “all‐in‐one” photodynamic theranostic nanoemulsion has simple composition, remarkable theranostic efficacy, and novel treatment pattern, and thus presents an intriguing avenue to developing clinically translatable theranostic agents.

Hyperpolarized xenon MR is effective for quantitative and comprehensive global evaluation of pulmonary function and structural changes without the use of radiation. This may open the door for its use in the diagnosis of lung diseases that are related to gas exchange. Magn Reson Med 76:408-416, 2016. © 2015 Wiley Periodicals, Inc.